Abdominal aorticaneurysms (AAA) occur in more than 10 000 people each year in the United States(Park, Park, Kim, Cho, Ahn, & Jae, 2015). According to Wadgaonkar, Black, Weihe, Zimmerman, Fishman, and Johnson(2015), “an abdominal aortic aneurysm is a pathological dilation of theabdominal aorta to more than 3 cm in the greatest diameter”. A prompt diagnosis is imperative. Without it, the disease will advance and ifuntreated can result in serious health issues and often death (Baker, Atlas& Afendulis, 2008). A mortality rateof 75-90 percent is expected when an AAA ruptures and the correct treatment isnot administered (Park et al.
, 2015). It is critical that an accurate diagnosis ismade and a precise evaluation of the state of the AAA is obtained (Park et al.,2015). Many image modalities can be usedto diagnose an AAA but computed tomography angiography (CTA) is the favouredimaging modality of choice (Taheri, Haghighatkhah, Pourghorban & Hosseini,2013). A CTA requires an intravenous injection ofcontrast media and therefore patients must be screened for a previous historyof a contrast allergy (Furlow, 2012).
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Patients with a previous mild allergy must be pre-medicated and thosewith a severe allergy will have to use an alternate modality for diagnosis(Iyer, Schopp, Swanson, Thapa & Phillips, 2013).Comparisonof Methods to Diagnose an AAAUltrasonography (US),magnetic resonance imaging (MRI), conventional radiography and computed tomography(CT) are image modalities used to diagnose an AAA (Park et al., 2015). An ultrasound is often used since it a cost effectivetest to perform and is a suitable means to check the enlargement of a bloodvessel (aorta) (Park et al.
, 2015). SeeFigure 1. Park et al.
, (2015) furtherexplains ultrasound imaging is used to diagnose an AAA because it isnon-invasive which means it requires no needles or injections. It is readily available at most hospitals anddoes not use any ionizing radiation (Park et al., 2015). However, patients’ body habitus (obesity) andintestinal gas can compromise the visualization of the aorta in an US exam(Anderson, 2001). Another technique todiagnose an AAA is the use of CT with the administration of contrast media calledcomputed tomography angiography (CTA) (Baker et al., 2008). See Figure 2.
This procedure is more invasive than ultrasound because it requires thepatient to have contrast media injected intravenously in order to visualizearteries, blood vessels and tissues (Furlow, 2012). With the use of CT technology and contrastmedia, image data of these structures can be reconstructed into 2 dimensional(2D) and 3 dimensional (3D) representations (Furlow, 2012). See Figure 3. Unlike US, CT provides information about the nearby vascular anatomy andstructures and this is information is necessary for treatment planning(Anderson, 2001). Magnetic ResonanceAngiography (MRA) is also another method to diagnose an AAA (Anderson, 2001). See Figure 4. Studies done comparing the results of MRA with CTA scans have shown MRAsto be a concrete method of diagnosis (Anderson, 2001).
Anderson (2001) also states, MRI scanners arevery expensive and are restricted in availability. MRA to visualize an AAA is also invasivebecause it requires an injection of Gadolinium (Anderson, 2001). Patients with metal clips, pacemakers orother metallic devices are unable to have a MRI. These drawbacks do not make MRI the bestchoice for an AAA diagnosis (Anderson, 2001).
Conventional angiography is an interventional radiographic procedure inwhich a catheter is used to the injected contrast media into the aorta todiagnose an AAA (Baker et al., 2008). See Figure 5. This procedure isvery invasive and has high rate of complications that could belife-threatening, such as an embolus becoming lodged and blocking the bloodvessel (Baker et al., 2008).
CTA has theability to validate the precise extension of the aneurysm (Taheri et al.,2013). The accuracy ofdetermining an AAA using CT is about 90 percent which is high compared to US,which has an accuracy of 80 percent (Park et al., 2015). As CTA is becoming the method of choice todiagnose an AAA, in the future it may fundamentally replace conventionalangiography (Taheri et al., 2013). Therefore, a CTA is the gold standard for thedetection of an AAA due to its high accuracy, quick image acquisition,availability and demonstration of surrounding anatomy (Taheri et al., 2013).